1 8 Practical Plant Biology. 



rose-coloured vacuole and the wall. This layer may at some places be thicker 

 and may be seen to be colourless. In one of these thicker places the nucleus 

 may occasionally be seen. 



When your sketch is made replace the low power and apply a drop of a 

 10 per cent, salt solution to the edge of the cover. Be careful not to let the 

 salt solution run over it and try not to displace the slide. In a few minutes 

 you will observe the plasmolysis of the cells. This will be apparent even 

 with the low power. Notice that the colour of the vacuoles becomes much 

 more intense, and that the pigment forms globules within the cells. If your 

 cover is still quite clean put on your high power. Find again the group of 

 cells you sketched previously and make a new sketch, noting the changes 

 which have come about. 



Next replace the low power, remove the slide, take off the cover-glass and 

 lift the specimen into a small glass of clean water. Mount it afresh in a drop 

 of clean water and cover. You will now be able to observe that many of the 

 plasmolysed cells will gradually recover their original condition. 



Heat a specimen mounted in water and one mounted in 10 per cent, salt 

 solution cautiously over a Bunsen flame. When the slide becomes unpleas- 

 antly hot to the touch, examine with the microscope. Note any changes you 

 observe in the colour of the vacuole or in the appearance of the protoplasm. 



